1 /*
   2  * Copyright (c) 2010, 2014, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package javax.lang.model.util;
  27 
  28 import javax.lang.model.element.*;
  29 import javax.annotation.processing.SupportedSourceVersion;
  30 import javax.lang.model.SourceVersion;
  31 import static javax.lang.model.SourceVersion.*;
  32 
  33 
  34 /**
  35  * A scanning visitor of program elements with default behavior
  36  * appropriate for the {@link SourceVersion#RELEASE_7 RELEASE_7}
  37  * source version.  The <code>visit<i>XYZ</i></code> methods in this
  38  * class scan their component elements by calling {@code scan} on
  39  * their {@linkplain Element#getEnclosedElements enclosed elements},
  40  * {@linkplain ExecutableElement#getParameters parameters}, etc., as
  41  * indicated in the individual method specifications.  A subclass can
  42  * control the order elements are visited by overriding the
  43  * <code>visit<i>XYZ</i></code> methods.  Note that clients of a scanner
  44  * may get the desired behavior be invoking {@code v.scan(e, p)} rather
  45  * than {@code v.visit(e, p)} on the root objects of interest.
  46  *
  47  * <p>When a subclass overrides a <code>visit<i>XYZ</i></code> method, the
  48  * new method can cause the enclosed elements to be scanned in the
  49  * default way by calling <code>super.visit<i>XYZ</i></code>.  In this
  50  * fashion, the concrete visitor can control the ordering of traversal
  51  * over the component elements with respect to the additional
  52  * processing; for example, consistently calling
  53  * <code>super.visit<i>XYZ</i></code> at the start of the overridden
  54  * methods will yield a preorder traversal, etc.  If the component
  55  * elements should be traversed in some other order, instead of
  56  * calling <code>super.visit<i>XYZ</i></code>, an overriding visit method
  57  * should call {@code scan} with the elements in the desired order.
  58  *
  59  * <p> Methods in this class may be overridden subject to their
  60  * general contract.  Note that annotating methods in concrete
  61  * subclasses with {@link java.lang.Override @Override} will help
  62  * ensure that methods are overridden as intended.
  63  *
  64  * <p> <b>WARNING:</b> The {@code ElementVisitor} interface
  65  * implemented by this class may have methods added to it in the
  66  * future to accommodate new, currently unknown, language structures
  67  * added to future versions of the Java&trade; programming language.
  68  * Therefore, methods whose names begin with {@code "visit"} may be
  69  * added to this class in the future; to avoid incompatibilities,
  70  * classes which extend this class should not declare any instance
  71  * methods with names beginning with {@code "visit"}.
  72  *
  73  * <p>When such a new visit method is added, the default
  74  * implementation in this class will be to call the {@link
  75  * #visitUnknown visitUnknown} method.  A new element scanner visitor
  76  * class will also be introduced to correspond to the new language
  77  * level; this visitor will have different default behavior for the
  78  * visit method in question.  When the new visitor is introduced, all
  79  * or portions of this visitor may be deprecated.
  80  *
  81  * @param <R> the return type of this visitor's methods.  Use {@link
  82  *            Void} for visitors that do not need to return results.
  83  * @param <P> the type of the additional parameter to this visitor's
  84  *            methods.  Use {@code Void} for visitors that do not need an
  85  *            additional parameter.
  86  *
  87  * @see ElementScanner6
  88  * @see ElementScanner8
  89  * @see ElementScanner9
  90  * @since 1.7
  91  */
  92 @SupportedSourceVersion(RELEASE_7)
  93 public class ElementScanner7<R, P> extends ElementScanner6<R, P> {
  94     /**
  95      * Constructor for concrete subclasses; uses {@code null} for the
  96      * default value.
  97      */
  98     @SuppressWarnings("deprecation") // Superclass constructor deprecated
  99     protected ElementScanner7(){
 100         super(null);
 101     }
 102 
 103     /**
 104      * Constructor for concrete subclasses; uses the argument for the
 105      * default value.
 106      *
 107      * @param defaultValue the default value
 108      */
 109     @SuppressWarnings("deprecation") // Superclass constructor deprecated
 110     protected ElementScanner7(R defaultValue){
 111         super(defaultValue);
 112     }
 113 
 114     /**
 115      * This implementation scans the enclosed elements.
 116      *
 117      * @param e  {@inheritDoc}
 118      * @param p  {@inheritDoc}
 119      * @return the result of scanning
 120      */
 121     @Override
 122     public R visitVariable(VariableElement e, P p) {
 123         return scan(e.getEnclosedElements(), p);
 124     }
 125 }